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stevecarsonr at 20:47 PM on 9 February 2010Working out future sea level rise from the past
Hello GFW, thanks for the welcome. And yet, response under #10 is maybe really really clear to someone who has studied the subject. But for the seekers it is one more piece of information and "hmm, how to weigh it up in the light of other things I have read?" Sometimes it is helpful to find out I am stupid, kind of a "wake up call". Some people have less thick skins and retreat. I'll be sure to study this (to me) new paper. Being slow it will take me a while to absorb it, so should I not ask questions until all papers referenced are fully understood? Because by then the debate is over and I have to wait until next time to ask my questions. But once again, it would be a shame if people with questions left early and missed the interesting stuff.Response: I will say it's not my intent to alienate any readers. Maybe I was a little snippy in my response to comment #17. As time goes on, I have made more effort to use less labelling and more focus on scientific arguments. Nevertheless, it's important that people are made aware of the dangers of a narrow focus that ignores the broader picture - lest they be misled by this practice. I will endeavour to communicate this message in a less alienating fashion.
By the way, the results of the Church 2008 paper have been available on the "sea levels aren't rising" page since I posted on the topic in May 2009. What I should've done was link to that page in my responses to #10 and #17 - I have now corrected that oversight. -
GFW at 20:28 PM on 9 February 2010Working out future sea level rise from the past
stevecarsonr, We welcome inquisitive and truly skeptical thought. The response to #17 was to someone making the "I don't see it in local raw data" argument, which really is a frequent device employed by deniers-who-call-themselves-skeptics. The person who wrote #17 could have looked at the response under #10, which is pretty darn clear. -
GFW at 20:24 PM on 9 February 2010Working out future sea level rise from the past
Arjen, I second what Riccardo says. Plan to deal with 1-2 meters by 2100, hopefully near the lower end of that, but an engineer has to be cautious... In a few more decades we'll have a much better idea what the rate of sea level rise will be in coming centuries. I'm thinking 2m/century from 2100 to 2600, although it could be less if we combat the CO2 problem aggressively. -
RSVP at 20:21 PM on 9 February 2010Working out future sea level rise from the past
"Berényi Péter at 02:59 AM on 9 February, 2010 Orbital eccentricity variations has no effect on annual average "solar radiative forcing". It is only the seasonal distribution of incoming radiation which changes." I do not see it this way. The more eccentric the orbit, the less time spent around the perihelion, and more time spent around the aphelion. This to me, would seem would favor cooling... comets being an example of this taken to the extreme. -
stevecarsonr at 20:13 PM on 9 February 2010Working out future sea level rise from the past
Re the response to #17: "..the one thing most skeptic arguments have in common is a tendency to focus on narrow pieces of the puzzle rather than step back and take in the broader picture.." Perhaps the information is not so easy to find. Perhaps "skeptics" are seeking information but not being climate scientists don't know where to find the latest research. I have been interested in this subject for a while - I've read about ocean heat content, I've read Willis, I've read Levitus - but I don't think it is easy to get to the bottom of. But if you want to run down "skeptics" you are welcome to do so, it's your website. But less "skeptics" will spend time here.. -
Riccardo at 20:09 PM on 9 February 2010Working out future sea level rise from the past
Arjen, the dynamics of ice sheets it not well known. The "linear" part of the response is relatively slow so I would expect that on average the melting of significant part of Greenland and/or West Antarctica will take several centuries. If i were a Dutch engeneer i'd not think about the 6 m for now.. But, i guess, even one or two meters in a century might be challenging and this rate is now believed to be possible. You should also consider that sea level rise is not uniform and as far as i remember measurments in the Netherland have show a smaller rate than the global average. You might be interested in this study: The Netherlands under a 5 m sea level rise. -
Berényi Péter at 18:37 PM on 9 February 2010Working out future sea level rise from the past
You can check sea level history for individual tide gauges. NOAA - Tides & Currents Mean Sea Level Trends for Global Network Stations http://tidesandcurrents.noaa.gov/sltrends/sltrends_global.shtml Acceleration is invisible.Response: As stated often on this website, the one thing most skeptic arguments have in common is a tendency to focus on narrow pieces of the puzzle rather than step back and take in the broader picture. This comment is a classic example. One could take a few random selections of local tidal gauges as an indicator of global sea levels. Or one could look at peer-reviewed analysis that uses a global network of tidal data, taking into account local tectonic movements, compacting sediments and vertical land movement due to geological processes, combined with independently measured satellite observations (Church 2008). -
Arjen at 18:36 PM on 9 February 2010Working out future sea level rise from the past
As a Dutch engineer working in coastal construction, I'm very interested at the speed of mean sea level rise. What time frame are we talking about when we consider a 6 meter mean sea level rise? Even a 2 meter rise in 90 years is a very sobering thought for me. That would basically mean a complete redesign and the rebuilding/extension of all storm surge infrastructure and of about all ports. Even for rich countries that have the know-how, like the Netherlands, that is a major undertaking. When I try to contemplate a 6 meter mean sea level rise for only the port and city of Rotterdam, it boggles my mind. If it is feasible, it certainly would not be recognizable as the city and port it is today. -
Timothy Chase at 18:00 PM on 9 February 2010Could climate shifts be causing global warming?
PS I figure seeing is believing, so I am including a link that may be of interest. The dark redder patches in the following satellite image are where there are higher levels of carbon dioxide at 8 km, and consequently the radiation that escapes to space gets emitted at higher, cooler altitude, decreasing the amount of thermal radiation that makes it to space at a wavelength of 15 ?m: Measuring Carbon Dioxide from Space with the Atmospheric Infrared Sounder http://airs.jpl.nasa.gov/story_archive/Measuring_CO2_from_Space/ And as you can see, the levels of carbon dioxide are highest where the winds would carry the gas away from more heavily populated areas (e.g., the east and west coasts of the United States) prior to dispersing it throughout the atmosphere. On this page you have an image of the distribution of carbon dioxide from July 2003 and July 2007: PIA11186: AIRS Global Distribution of Mid-Tropospheric Carbon Dioxide at 18-13 km Altitudes http://photojournal.jpl.nasa.gov/catalog/PIA11186 As you can see from either image, higher levels of carbon dioxide reduce the rate at which thermal radiation escapes to space -- and as you can see when the two images are side-by-side, there are higher levels of carbon dioxide in 2007 than in 2003.Response: Thanks for the links, here for the especially lazy reader are the images (but I recommend you click the links anyway):
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Doug Bostrom at 16:50 PM on 9 February 2010Working out future sea level rise from the past
Berényi Péter at 11:39 AM on 9 February, 2010 Just to clarify a couple of your points... While it is true that in certain areas affected by the last episode of continental glaciation local mean sea level is increasing due to isostatic adjustment, this effect should not be confused with eustatic or steric sea level rise, which of course are observed globally. Isostatic sea level is a special case that is regional in extent and should not be confused with sea level changes due to thermal expansion or bulk addition of water to the ocean. Ocean heat content does in fact continue to rise. Look at trends, as with any longitudinal data set don't be fooled by individual years: Ocean Heat Loads of heat being added there. More and more in the future the ocean will be responding with warnings on the debt we're running up in the way of heat storage. -
Timothy Chase at 16:49 PM on 9 February 2010Could climate shifts be causing global warming?
Continuing with the above comment... Now a little bit about absorption spectra may be in order. First, absorption occurs in bands and bands consist of lines, but the lines themselves are not infinitely thin. They have a wavelike shape to them -- and this helps to understand why even at the surface increasing the partial pressure of a given greenhouse gas generally has the capacity to increase the optical thickness of the atmosphere. At sufficiently low partial pressures of a given greenhouse gas, increasing the partial pressure of the gas will result in a linear increase in the absorption. This will occur right around the center of a sharp peak of absorption. However, as one increases the partial pressure of the greenhouse gas the central peak becomes saturated, but increasing the partial pressure causes the peak to broaden. The range over which absorptivity is nearly 1 broadens, but there are the slopes over which absorptivity gradually drops towards zero. Thus at moderate levels of saturation absorption increases as the square root of the partial pressure. At the surface, methane's central peaks are only moderately saturated, so absorption increases as the square root of the partial pressure -- and consequently so does radiative forcing. At still higher levels saturation more of the additional absorption takes place in the "wings" of the spectral "line." At this point absorption increases as the logarithm of the concentration. This is where both carbon dioxide and water vapor are at, and as a consequence forcing is a logarithmic function of their partial pressures. Please see for example:For gases such as halocarbons, where the naturally occurring concentrations are zero or very small, their forcing is close to linear for present-day concentrations. Gases such as methane and nitrous oxide are present in such quantities that significant absorption is already occurring, and it is found that their forcing is approximately proportional to the square root of their concentration. For carbon dioxide, parts of the spectrum are already so opaque that additional molecules are almost ineffective; the forcing is found to be only logarithmic in concentration. http://www.global-climate-change.org.uk/6-5-1.php
Here are some posts over at Eli's which show how the spectral absorption of carbon dioxide varies according to temperature and pressure — and which point you to an online tool where you can create your own graphs: Temperature Wednesday, July 04, 2007 http://rabett.blogspot.com/2007/07/temperature-anonymice-gave-eli-new.html Pressure broadening Thursday, July 05, 2007 http://rabett.blogspot.com/2007/07/pressure-broadening-eli-has-been-happy.html High Pressure Limit. . . . Sunday, July 08, 2007 http://rabett.blogspot.com/2007/07/high-pressure-limit.html However, what matters most in terms of the enhanced greenhouse effect under current anthropogenic global warming isn't increased absorption near the surface but rather how the effective radiating altitude rises with the increasing partial pressure of carbon dioxide. Most of the relevant spectra in which carbon dioxide acts is already saturated by water vapor at the surface, thus if one were to only increase the partial pressure of carbon dioxide at the surface it would have very little effect. However, water vapor tends to stay much closer to the surface than other gases. It has a scale (or "e-folding") height of roughly 2 km as opposed to 8 km which would be more typical of other gases, including carbon dioxide. It is at the higher altitudes that raising the level of carbon dioxide will really matter. The effective radiating temperature of the earth is roughly -17°C. This corresponds to an effective radiating altitude of roughly 5 km. But by raising increasing the partial pressure of carbon dioxide at the surface, one increases the partial pressure of carbon dioxide at higher altitudes, increasing its absorptivity and therefore raising the altitude where of the atmosphere to thermal radiation one increases the altitude where a photon is radiated without being reabsorbed, that is, where its energy is radiated for the last time and finally escapes to space. However, the higher the altitude the colder it gets -- reducing the emission. Consequently the we have a radiation imbalance in which more radiation is absorbed by the earth's climate system than is emitted to space as thermal radiation. The apparent (or "brightness") temperature of the earth -- as it is viewed at a distance -- decreases because less radiation is able to escape to space. But by the principle of the conservation of energy this implies that the actual amount of energy in the earth's climate system is increasing. For a new thermodynamic equilibrium to be achieved the temperature of the effective radiating layer must increase. But what this implies is that the rate at which radiation is emitted at the surface must increase. How much? Interestingly enough, the temperature drops roughly as a linear function of altitude, and the rate at which temperature drops with altitude. As altitude increases, the atmospheric pressure decreases. Consequently a parcel of air will expand and in expanding it will lose potential energy and cool. And assuming a constant relative humidity, the rate at which temperature decreases with increasing altitude - known as the lapse rate - will remain roughly constant under an enhanced greenhouse effect. So if the effective radiating altitude rises by a certain distance, one can divide that distance by the lapse rate to arrive at the temperature. Tamino goes into this in more depth here: Lapse Rate, July 16, 2007 http://tamino.wordpress.com/2007/07/16/lapse-rate/ Prior to any feedbacks the warming of the surface turns out to be about 1°C per doubling of carbon dioxide. But of course at higher temperatures ice melts -- decreasing the albedo of the earth and increasing the absorption of sunlight. Likewise, water evaporates, with the absolute humidity at the earth's surface increasing by roughly 8% for each additional degree Celsius and roughly doubling for every ten degrees Celsius. Once one takes into account all the feedbacks doubling the partial pressure of carbon dioxide is more likely to raise the temperature by roughly three degrees Celsius. Incidentally, I would recommend checking out: A Saturated Gassy Argument 26 June 2007 http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument/ ... and: Part II: What Ångström didn't know 26 June 2007 http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument-part-ii/ Anyway, I hope this helps... -
Timothy Chase at 15:09 PM on 9 February 2010Could climate shifts be causing global warming?
CBDunkerson wrote in 27:"... in short, the emissivity of the Earth's atmosphere has decreased due primarily to the increase in carbon dioxide and the positive feedback effect that has with water vapor."
I think part of the problem here is that people may be equating emission and absorption with emissivity and absorptivity. Emission is the actual rate at which radiation is emitted, either independently of the frequency or in the case of spectral emissivity and spectral absorptivity as a function of the frequency of the radiation. In contrast, emissivity and absorptivity consist of the capacity to emit or absorb radiation, and particularly in the case of greenhouse gases it is important to speak not simply of emissivity or absorptivity, but of spectral emissivity and absorptivity -- as these are very much a function of the frequency -- as indicated by the specific absorption spectra of greenhouse gases. Emissivity and absorptivity are equal under local thermodynamic equilibrium, and as higher levels greenhouse gases increase absorptivity they also increase emissivity -- in the bands in which they act. However, the emission and absorption will typically not be equal. And as a matter of fact, local thermodynamic equlibrium means essentially that emission is independent of absorption as emission is simply a function of the intrinsic properties of matter and the temperature of matter. Please see:"local thermodynamic equilibrium – (Abbreviated LTE.) A condition under which matter emits radiation based on its intrinsic properties and its temperature, uninfluenced by the magnitude of any incident radiation. "LTE occurs when the radiant energy absorbed by a molecule is distributed across other molecules by collisions before it is reradiated by emission. LTE is needed for Planck's law and Kirchhoff's law to apply, and is typically satisfied at atmospheric pressures higher than about 0.05 mb. Laser radiation is an example of non-LTE emission." Glossary of Meteorology, American Meteorological Society http://amsglossary.allenpress.com/glossary/search?p=1&query=local+thermodynamic+equilibrium
The reason why emitted radiation is independent of incident radiation is because absorbed incident radiation is thermalized. Photons are absorbed by molecules that enter a quantized state of of excitation (e.g., bending or stretching which are jointly referred to as "vibrational," rotational, or rovibrational), but then the energy is lost due to collisions with the surrounding molecules before the molecule that absorbed the photon has a chance to spontaneously decay. At 20 mb, a molecule may already be undergoing perhaps a million collisions during the half-life of a given state of excitation. So the wavelength, intensity and angle of the incident radiation is more or less irrelevant. Typically, local thermodynamic equilibrium conditions remain in place until 70 km or above. At lower altitudes the high frequency of collisions will insure the equipartition of thermal energy, resulting in the brightness temperatures associated with different degrees of freedom (e.g., translational motion and a given mode of vibrational excitation) being equal and will be equal to the temperature associated with translational motion. However, at certain wavelengths it may begin to break down as low as 40 km -- at which point non-local thermodynamic equilibrium conditions may then apply. Under local thermodynamic equilibrium conditions, given the equipartition of energy, for each quantized state of excitation a certain number of molecules will always be in that of excitation at any given time. The spontaneous decay of such states of excitation are independent of the length of time that a given molecule has been in that state of excitation. As such a certain percentage of molecules will decay due to spontaneous radiation over any given period of time. Thus the thermalization of absorbed radiation -- in which almost all molecules that absorb photons lose energy through collisions rather than by emitting photons, collisions do not prevent photons from being emitted as such. * But what then are emissivity and absorptivity? Absorptivity is the easiest to define. It is the ratio of incident radiation that is absorbed by a given body, and in the case of spectral absorptivity refers to the ratio of incident radiation at a given frequency that is absorbed by the body. Thus the absorptivity of a true black body would be 1 at any given frequency as it would absorb all radiation. And it is in the context of this last statement that it is easiest to understand the definition of emissivity:"emissivity – The ratio of the power emitted by a body at a temperature T to the power emitted if the body obeyed Planck's radiation law." Glossary of Meteorology, American Meteorological Society http://amsglossary.allenpress.com/glossary/search?p=1&query=emissivity
Likewise, spectral emissivity is the ratio of radiation emitted at a given frequency by the body relative to the amount of radiation that would be emitted by a black body at that frequency. Anyway, for those who are interested, here is a derivation of Kirchoff's law for spectral emissivity and absorptivity: Radiative Transfer http://www.cv.nrao.edu/course/astr534/Radxfer.html The author shows why Kirchoff's law applies under thermodynamic equilibrium and then shows how this can easily be extended to local thermodynamic equilibrium conditions. -
Tony O at 15:04 PM on 9 February 2010Working out future sea level rise from the past
Just to add a little more uncertainty. From http://vulcan.wr.usgs.gov/Volcanoes/Antarctica/description_antarctica_volcanoes.html Despite its size, Antactica ranks below all other regions in number of dated eruptions, and only the Pacific and Atlantic Ocean regions have fewer historically active volcanoes. It's historical record is brief, and 75 percent of its eruptions are from this (last) century. Precise dating of past eruptions is difficult -- much of the landscape is glacier-covered, travel is daunting, and the wood needed for radiocarbon dating does not grow in this extreme climate -- and the region has the highest proportion of volcanoes with uncertain status. We had a couple of eruptions last century so I guess we will have a couple this century. Which ones and when might be a rather critical issue. Then we add to the mix that glacial melting increases volcanic activity. Could this affect the SLR this century? Of course then the pro polluters will blame the volcanoe. -
thingadonta at 14:53 PM on 9 February 2010Working out future sea level rise from the past
I'm just wondering if there is any studies on the depression of land from the extra weight of water over near-coastal areas with rising sea levels since the last ice age; it is well-known that the coast is still rising in areas formerly depressed by thick ice, I suspect that areas inundated by rising sea levels should also be subsiding, thereby raising sea levels in these areas further. -
stevecarsonr at 14:19 PM on 9 February 2010Working out future sea level rise from the past
I have a couple of questions. The first about the "Milankovitch" cycles. There is a nice page on wikipedia with the various cycles over 1M years, but does anyone know of a resource where the data is available in a higher resolution over the last 200,000 years? Second, noting in passing that the IPCC AR4 says there is a huge uncertainty in the ice melt (p339): "Estimates for the overall mass balance of the Antarctic Ice Sheet range from +100 to –200 Gt yr–1 (–0.28 to 0.55 mm yr–1 SLE) for 1961 to 2003, and from +50 to –200 Gt yr–1 (–0.14 to 0.55 mm yr–1 SLE) for 1993 to 2003." So the IPCC summary says we aren't sure about the sign. Of course we can take the mid point.. If temperature rises stopped today what would sea level be likely to be in 2100? -
Berényi Péter at 12:33 PM on 9 February 2010Could climate shifts be causing global warming?
CBDunkerson at 04:34 AM on 9 February, 2010: "and I'm not sure why you are suggesting otherwise" I tell you. Emissivity/absorptivity of materials depend on wavelength. Snow is white in the visible while pitch black (has high absorptivity) in IR. If you put more "greenhouse gases" (the ones having some absorptivity in IR, being transparent otherwise) above an IR-bright surface (which has low absorptivity in the infrared, like quartz sand), the scene starts to look "darker" from above in IR, i.e. the absorptivity is increased. So does emissivity, according to Kirchoff. Well. Your statement "the emissivity of the Earth's atmosphere has decreased due primarily to the increase in carbon dioxide" is not true. Carbon dioxide, as any other "greenhouse gas" increases emissivity. If global effective temperature is constant, average photosphere temperature should decrease. It has to decrease even more to achieve an imbalance between ASR & OLR, provided shortwave albedo (1-absorptivity) does not change. -
Bern at 12:12 PM on 9 February 2010Working out future sea level rise from the past
Berényi Péter: "Antarctica is gaining somewhat" Actually, John has covered that previously - the most recent measurements are indicating that Antarctica as a whole is losing ice mass, not gaining. -
Berényi Péter at 11:39 AM on 9 February 2010Working out future sea level rise from the past
CBDunkerson at 04:41 AM on 9 February, 2010: "The feedback effect, melting arctic sea ice decreasing the planet's albedo, has the same sensitivity regardless of what forcing is driving it" Not quite so. It depends on where this ice sheet is located and how large it is. In glacial times ice in the northern hemisphere came down to midlatitudes, see ice grooves in Central Park, NYC. The lack of ice there makes a huge impact on global albedo. The arctic, on the other hand, is in darkness for half a year anyway and mostly covered by low level clouds for the rest. Not much trend in albedo is observed. Part of current sea level rise is due to postglacial rebound, the reconfiguration of continental crust, ocean basins and mantle below. It would go on irrespective of any warming, at a constant rate (on millenial scale). As for thermal expansion of seawater, it can be measurable if it occurs above the thermocline. Below it the water is so cold, that the thermal expansion coefficient is negligible. However, OHC (Ocean Heat Contents) is not increasing in the upper 700 meter recently. Anyway, increasing sea level by the same amount through thermal expansion requires almost two orders of magnitude more energy than by melting continental ice sheets. There is not much trend observed in the volume of large icesheets. Greenland has a contribution of 1.3 cm/cy at most to sea level rise, which is negligible. A sudden meltdown of Greenland is impossible. Antarctica is gaining somewhat. No acceleration of sea level rise is observed at tide gauges since the beginning of XX. century. Sea level is rising: Do we know why? Mark F. Meier and John M. Wahr http://www.pnas.org/content/99/10/6524.full Satellite altimetry is calibrated to a set of tide gauges with a possible collective vertical drift. About historic sea levels from a different source: JOURNAL OF SALT-HISTORY Review of the International Commission for the History of Salt vol 7 1999 [CIHS] - ISBN 3-85093-023-8 SALT and the EVOLUTION of MONEY David Bloch http://www.salt.org.il/money.htmlResponse: Thanks for that link to Meier 2002 (isn't it refreshing that PNAS don't hide their papers behind a paywall). The paper states that "tide-gage observations show no statistically valid acceleration during the 20th century", citing research from 1992. However, later research using more recent measurements including satellite data finds that sea level rise has accelerated over the 20th Century (Church 2008):
The increase in sea level rise is even starker when all the water impounded in reservoirs is also taken into account (Chao 2008):
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yocta at 11:04 AM on 9 February 2010What the IPCC and peer-reviewed science say about Amazonian forests
What about other science organizations that make predictions not directly affiliated with the IPCC that I would expect have high standards of peer review? Or has the public forgotten about them (hopefully policy makers haven't) In the blog sphere on articles to do with climate change, people seem to jump right on criticizing the IPCC's credential in such a way that even if something is only slightly sketchy in one particular report then the IPCC then the whole of climate science is wrong. I remember reading about the physicist Richard Feynman defending an adult bar in court (which he attended regularly) and nobody attacked his science, now one man writes a raunchy novel and it makes headlines and suddenly the IPCC is perceived as a fraud. Mistakes are inevitable in science and happen all the time. I think, unfortunately that the major drawback with the IPCC is that in the public's point of view, the validity of climate science is tied so closely to any mistake, error or scandal (or even on people's characters). I think the number one thing for the next report the IPCC needs is PR training. -
Doug Bostrom at 09:08 AM on 9 February 2010The role of stratospheric water vapor in global warming
Berényi Péter at 08:59 AM on 9 February, 2010 Ok, I think I see what you're saying, key: 'Statistics of state variables lack time reversal symmetry, time series have skewed fractal structure. Energy release connected to topological reconfiguration. "Natural variability"' So just to clarify, are you saying that all of the temperature signal displayed by the collective global measurement system is being affected by residing in the mid-domain of a single overarching slip event? -
Berényi Péter at 08:59 AM on 9 February 2010The role of stratospheric water vapor in global warming
doug_bostrom at 04:37 AM on 9 February, 2010: "How does it apply to the case under discussion here?" Basically the climate system is also in a kind of equilibrium. It is not the same as thermodynamic equilibrium though, it requires exergy stream to be maintained (like sandstream in case of SAD). Equilibria like this are called steady state. With no sun, atmospheric temperature would drop below -230°C, collapsing it into a 10 m thick frozen layer. No climate at all. Systems like the sandpile are inclined to accumulate energy slowly, then release it in sudden bursts of varying magnitude. Kind of negative feedback, not the usual way, nonlocality in phase space. Bubbles in boiling water behave the same way. Abrupt energy concentration followed by gradual release seldom occur. Statistics of state variables lack time reversal symmetry, time series have skewed fractal structure. Energy release connected to topological reconfiguration. "Natural variability" In absence of metadata, actual jumps can be misidentified as instrumental slithers, by data homogenization spurious trend is introduced. Solomon event likely one major slip, global troposphere fold perhaps, many more can occur on all spatio-temporal scales. Sandpile Avalanche Dynamics with local positive feedback, i.e. the larger the pile gets the wider the slit on container opens, makes time series more even, counterintuitively. Multiscale dynamics is poorly captured by analytic models with fixed grid resolution. Ad hoc parametrization does not make it sound. -
Doug Bostrom at 08:54 AM on 9 February 2010Working out future sea level rise from the past
VeryTallGuy at 07:46 AM on 9 February, 2010 Short questions leading to a myriad of of risk and unknowns! Assuming that ocean heating remains reasonably constant, acceleration of rise is going to come down mostly to how glaciers and ice sheets behave. People are beavering away at that problem which of course is a bundle of contextual complexity. A crisp or even acceptably fuzzy answer just does not seem available right now. As to disruption, IMHO that depends a lot on how the next few decades of population growth proceed as well as how we choose to continue developing or not developing areas at risk from sea level increase. I guess "huge disruption" especially depends a lot on perspective, that is to say what's the angle between your line of sight where you live and the surface of the ocean. If you're seeing close to zero degrees there's some cause for concern. Take New Orleans as an edge case representing the worst case and there you have an example of a place where not even the slightest acceleration is going to be tolerable. NOLA is barely keeping its head above water as it stands, or that is to say the damage inflicted on it in the present context is barely supportable. Can the USACE dig any faster? Evidence says "no", not without a big shift in resources. If not and we see New Orleans gradually reduced to a shallow spot over the space of 50 years I suppose that's a big disruption, and it's reasonable to say it'll happen even without an acceleration. Move on to Holland. How much faster can -they- dig? What about Bangladesh? Rosy interpretations excepted, not a lot of dynamic range available there even without an acceleration, yet population growth keeps the pressure on at the seashore. It just does not seem like much acceleration is going to be tolerable. -
Riccardo at 08:51 AM on 9 February 2010Working out future sea level rise from the past
The problem with sea level rise is that we do not have enough resolution in the paleo data to assess rapid changes. So we are forced to consider the average behaviour, which is already bad enough. But it might be worse. Although we can not directly compare current climate with deglaciacion, ice sheets collapse proved to be able to produce the so called melt water pulses with sea level rise of the order of several meters/century. Current acceleration of large ice sheets in West Antarctica and Greenland sound much like the alarm bell. -
Tony O at 08:16 AM on 9 February 2010Working out future sea level rise from the past
Thanks for taking this topic up. To steal a quote "uncertainty is not your friend" -
Tony O at 08:10 AM on 9 February 2010Working out future sea level rise from the past
"To minimize the influence of any bias in individual points, we infer MIS-5e sea-level fluctuations after smoothing the data with a moving 750 yr gaussian filter" Does not this mean that short rapid increases in sea level rise are averaged out. In all the papers I could access I noted a significant degree of uncertainty on timing. We need to be overestimating the sea level rise not underestimating. If we overestimate it means we will be ready early. -
VeryTallGuy at 07:46 AM on 9 February 2010Working out future sea level rise from the past
By my very rough reading of the graph we have: Maximum rate of rise at the end of glaciation = 10mm/yr (40m in 4000 years) Rate this century predicted by AR4 = 1.8 - 5.9mm/yr Rate this century including best understanding of ice sheet dynamics = 7.5 - 20mm/yr Current rate (satellite data) = 3mm/yr Which prompts a couple of questions: 1) When could we reasonably expect to see a statistically significant rise in rate of sea level measurements ? 2) It's really the rate of warming that matters, not it's magnitude (even 6 degrees over a few million years wouldn't matter much). What is the maximum rate of rise we can cope with without huge disruption ? -
Russ_Brown at 06:52 AM on 9 February 2010The role of stratospheric water vapor in global warming
Solomon et al state: "However, the trend in global surface temperature has been nearly flat since the late 1990's despite continuing increases in the forcing due to the sum of the well-mixed greenhouse gases (CO2, CH4, halocarbons, and N2O), raising questions regarding the understanding of forced climate change." The mean temperature increments (relative to the reference level) were: +0.46 deg C for '95-99 +0.57 deg C for '00-04 +0.68 deg C for '05-09 The rate of change was not "nearly flat". -
Doug Bostrom at 06:26 AM on 9 February 2010Working out future sea level rise from the past
Further to Geo Guy and CBDunkerson, here's an interesting snippet from the just-past AGU meeting discussing some underlying details (pun, sorry!). Look for "Antarctic Glacier Off Its Leash": Pine Island Glacier Geo Guy, timing of the eccentricity versus seasons counts for much. -
Riccardo at 05:31 AM on 9 February 2010Increasing CO2 has little to no effect
matt sykes, i forgot to add that in any case absorption of sunlight is included in the radiative transfer codes. -
Riccardo at 05:10 AM on 9 February 2010Increasing CO2 has little to no effect
matt sykes, from about 2 to 8 microns IR from the sun is absorbed by water vapour, CO2 has no influence. Also, you still integrate over the whole IR, not just the CO2 bands. At 15 microns, instead, the atmosphere is transparent and the CO2 band is centered at the peak of the thermal emission, the overall effect is then larger. Go back to your Plank calculator but this time plugin in the right numbers for a meaningfull comparison. The visible is 0.4-0.8 microns, the CO2 absorbtion band is centered at 15 micron and with a width of 2 microns (14-16 microns, in reality it is much narrower than this). You end up with a ratio of the energy coming from the sun in the CO2 related absorption band and the visible of the order of 10^-4. Negligible. #6 In this very same post you can see absorption from CO2, you must be wrong. Indeed, the radiation abosrbed is re-emitted isotropically and part of it will be converted directly into heat in the atmosphere. At the top of the atmosphere you will see less radiation. I'd suggest to read how an idealized model works. -
CBDunkerson at 04:41 AM on 9 February 2010Working out future sea level rise from the past
Geo Guy, you've got your terminology slightly off. ice SHEET - Ice resting on land. ice SHELF - Ice floating on water. The breakup of floating ice shelves does not raise sea levels. The collapse of ice sheets off of land and into the oceans does. Berenyi, since your comment seems to have nothing to do with the article above I'll assume you are still objecting to John's statement in the prior article that climate sensitivity applies to both internal and external forcings. In your response here you argue that forcings are different. Congratulations, that is true. However, an orbital eccentricity which causes arctic sea ice to melt is going to have exactly the same climate sensitivity as warm ocean currents melting that arctic sea ice... or CO2 induced warming. The feedback effect, melting arctic sea ice decreasing the planet's albedo, has the same sensitivity regardless of what forcing is driving it. -
Doug Bostrom at 04:37 AM on 9 February 2010The role of stratospheric water vapor in global warming
Berényi Péter at 03:45 AM on 9 February, 2010 That's a fascinating experiment and one I think would be fun to do with my son. Changing some of the properties and watching what happens to the distribution would be pretty interesting. But the system you describe is in equilibrium; the aperture the sand is passing through is constant, the gravitation is constant, the granule size is constant. How does it apply to the case under discussion here? I don't follow the analogy but it could be I'm just dense. -
CBDunkerson at 04:34 AM on 9 February 2010Could climate shifts be causing global warming?
Berenyi wrote: "Albedo is supposed to be connected to short wave absorptivity while the emissivity you are talking about is in thermal infrared. They are very different beasts (5778 K vs. 255 K)." First, 5778 K and 255 K are the effective temperatures of the Sun and Earth, as determined by the wavelengths of radiation which they emit. The short wave radiation (aka 'visible light') from the Sun which is not reflected (based on the albedo of the Earth) is instead absorbed, heats the absorbing material, and is thus re-emitted as the thermal infrared radiation you describe as a 'very different beast'. The incoming and outgoing radiation are intrinsically linked regardless of the shift in wavelength... and I'm not sure why you are suggesting otherwise. The changing composition of the Earth's atmosphere is obviously causing changes in its emissivity... indeed, this effect has been measured down to the level of being able to determine the specific wavelengths impacted. Your argument that it is impossible for atmospheric emissivity to change given the LTE of the lower atmosphere is incorrect because LTE refers to equilibrium of the actual MASS of the atmosphere... photons absorbed and re-emitted by the electromagnetic fields of the greenhouse gases may pass through the LTE without impacting it at all. -
Doug Bostrom at 04:12 AM on 9 February 2010What the IPCC and peer-reviewed science say about Amazonian forests
Charlie A at 19:31 PM on 8 February, 2010 "The IPCC could have avoided most of the mentioned problems with a couple interns or grad students working as "fact checkers". The fact checker job is simply to see that each statement is supported by original source material." Perhaps a bit more than a couple of interns. This is a critical document and really does need to be reliable. I've not gone over the review process in detail so I'm speculating just a bit here, but from what I've learned of the Himalaya glacier business it seems that the chain of command on the review process petered out, not leading to an editor with sole focus on quality control but instead to a multi-tasking professional with primary responsibilities in another arena. I'm acquainted as the proverbial fly on the wall with the role of volunteer peer editors (where the scientifically important editing is done) in the academic publication process. That duty is very demanding and picky, requires a lot of time to be done right and yet is shoehorned into the middle of an active career ipso facto. People asked to be editors are generally productive researchers so it's almost axiomatic they are overcommitted individuals. So (harumph) if -I- were running the process I'd make sure there was a single person for each domain section of the report with an existential interest in making sure the quality control you mention was completed properly. A bit of a conundrum, because that person is going to need a good general grasp of the field in question yet will need to devote slavish attention to the task at hand. Perhaps this could be a career candle for emeritus professors? Unfortunately many of those tend to continue publishing until they drop dead, but after all this is a distinguished publication, akin to a literature review or compendium book. -
Geo Guy at 04:08 AM on 9 February 2010Working out future sea level rise from the past
There are two points I want to make. First of all, ice sheets such as those that have broken off from Antarctica have a nil effect on the sea levels when they melt because the weight of the ice has already displace the water it is floating on. As for the constant moving of ice such as can be observed in Alaska, the motion is a regular part of the glacial activity and takes place when the mass of the glacier in its middle, increases, forcing the glacier to spread out towards its extremities. Secondly when the orbit of a body becomes more elliptical, then there are sections of the orbit that are further from the sun than they would be if the orbit was circular and hence would be further from the son when positioned at the long elliptical axis. -
Berényi Péter at 03:45 AM on 9 February 2010The role of stratospheric water vapor in global warming
doug_bostrom at 04:26 AM on 6 February, 2010 "To make a case for that you need to show it with details" OK. Self Organized Criticality (SOC) describes the Climate/Weather system's state well. It is a non equilibrium thermodynamic system with a huge input stream of exergy. Sandpile Avalanche Dynamics is a simple (understandable) conceptual model of such systems. There is a table on a digital scale which records the weight as a time series. A container above, with a tiny hole on the bottom is full of dry sand. The sand slowly piles up on the table. As soon as the pile gets too steep, some sand shifts down to the bottom in an avalanche. Sooner or later the table gets "saturated", avalances go over the edge, sand sprays to the floor. It is swept up and put back to the container. The sytem gets into a "steady state", the weight fluctuates around an equilibrium value. However, the statistics of the time series is far from trivial. One has avalanches of all sizes, small and large, the magnitude distribution following a power law. Epochs of gradual increase are followed by sudden drops of variable size. If you apply "Standard Normal Homogeneity Test" (SNTH), identify discontinuities, adjust time series accordingly, you are left with an ever increasing sandpile on the table, defying common sense. The reason is that dynamics is not symmetric to time reversal. In this respect it is same as climate. Detailed enough? -
Berényi Péter at 02:59 AM on 9 February 2010Working out future sea level rise from the past
Orbital eccentricity variations has no effect on annual average "solar radiative forcing". It is only the seasonal distribution of incoming radiation which changes. Depending on the phase, it can make northern summers warmer than average and winters colder. Or the other way around. Carbon dioxide has no such seasonal effect, or, if anything, it makes seasons more even. The two "forcings" are not comparable. -
HumanityRules at 01:55 AM on 9 February 2010Could climate shifts be causing global warming?
There seems to be two separate experiments expressed in the three papers and I'm not sure they are related. Tsonis et al 2007 and Swanson & Tsonis 2009 develop the idea of syncronised NH climate. (Source for fig 1) While Swanson & Tsonis 2009 uses preexisting climate models to extract the 'natural variability" in the climate (source for fig 2) Strangley Swanson & Tsonis 2009 doesn't reference any of the science in either of the other two papers, only picking out a comment about policy implications. In what way does the finding in Swanson & Tsonis 2009 (i.e. Fig 2) rely on the identification of syncronisation in the other two papers? It looks to me not at all. All Swanson & Tsonis 2009 does is pick apart natural and anthropogenic temperature change based on older climate models. While the synchronisation theory suggests that climate over the whole of teh NH are at times linked. The paper trying to tease out the natural variability signal could only identify this in two regions (tropical Pacific and the North Atlantic). John could you explain why you link the work in Fig1 directly to Fig 2 when the original authors make no attempt to do this? -
ConcernedCitizen at 01:32 AM on 9 February 2010Increasing CO2 has little to no effect
@Ricardo. Just found an online Plank law calculator. For wavelenghts betweem 3.9 and 4.1 microns the sun produces 340,000 times as much energy as the earth. This is close to my orevious estimate of 400,000. So, what does all this SOlar IR energy do in the atmosphere in comparison to terrestrial IR? Is it blocked in the uper atmosphere, does it saturate the CO2? Is it absorbed and re-emmitted into space in tha same way as terrestrial IR is absorbed and re-emmitted to the surface? If so, and given that it is 400,000 times stronger the effect of CO2 is to actually reduce the IR at the surface, not increase it. -
ConcernedCitizen at 01:18 AM on 9 February 2010Increasing CO2 has little to no effect
#3 2, 4.3 and 15 microns in fact. The first of which is well inside the graph I linked to. This one shows even more clearly how cooler bodies release less IR than hotter ones. http://quantumfreak.com/wp-content/uploads/2008/09/black-body-radiation-curves.png Mind you, this isnt surprising. A piece of metal at 30 `C will be warmer to the hand than one at 20`C becaue it is producing more IR. As for calculating the IR of a particular frequency emitted by an object at a particular frequency, I dont know how to, perhaps you could direct me to the relevant formula althogh I think we have establisged that hotter bodies do produce more IR than cooler ones. #4. You said "You clearly still get cooling at night but not all of the energy absorbed during the day" I understodd this to mean that the energy absorbed during the day cane be entirely lost at night. If you meant something else then I appologise for misunderstanding you although my understanding seems logical still. #5 And there is clearly something else at play in the Arctic too since it is only as warm as it was in the 1930's. But, thats the complexity of climate! #6 But you cant fell from space what is happening to the energy absorbed by CO2. It is either re-emmitted at the same frequency and thus bounces around the atmosphere fomr mollecule to mollecule or it is emmitted as broad band radiation in which case all of it except the 8% absorbed by CO2 will end up released to space. So from a sensor looking down from space you will never see the CO2 absorbed energy, ie those banmds will be missing from the spectrum, regardless of the re-emmission mathod. However, if the re-emission is of broad band, ie black body radiation, than CO2 effectively converts narrow band to broad band radiation. This will increase the levels of non absorbed energy transmitted to space, which is what one of the other respondants above stated had occured in the later sattelite measurement. -
oracle2world at 00:59 AM on 9 February 2010Could climate shifts be causing global warming?
This isn't exactly much of an argument against man-made global warming. Folks need to move on to the more robust ones. -
Arkadiusz Semczyszak at 00:11 AM on 9 February 2010What the IPCC and peer-reviewed science say about Amazonian forests
"avorite" - favorite obvious -
Arkadiusz Semczyszak at 00:09 AM on 9 February 2010What the IPCC and peer-reviewed science say about Amazonian forests
My job is agro-meteorology. I think warming it’s positive - in sum, for agriculture - in global. Let's do the simplest analysis of the older "warm-up’s", for example, based on the (above-mentioned) book by Stanley: 1. The higher the temperature (f. e. more than 2 deg more than now) that the greater part of the Earth's surface, are similar ecosystems. 2. The higher the temperature - the weaker zoning plant. 3. The higher the temperature - the less the deserts ... 4. Conclusion: The higher the temperature the more anticyclones (smaller pressure gradient?); increasing the area covered by a thick layer of cirrocumulus - tropical and maybe subtropical thermostat? Warming Climate is simpler in operation? P.S. Important observation: Changes are not linear: my "avorite" example - Mongolia - current warming: It takes 60-80 years there is drought, when the former was about 1 deg warmer than now, reaching there monsoons ... -
Berényi Péter at 23:41 PM on 8 February 2010Could climate shifts be causing global warming?
CBDunkerson at 22:24 PM on 8 February, 2010: "the emissivity of the Earth's atmosphere has decreased due primarily to the increase in carbon dioxide" Wait a minute. Albedo is supposed to be connected to short wave absorptivity while the emissivity you are talking about is in thermal infrared. They are very different beasts (5778 K vs. 255 K). So. Are you telling us that overall IR emissivity of Earth is decreasing due to GHGs? It would be interesting, since atmosphere below 50 km (30 miles) is in LTE (Local Thermodynamic Equilibrium). In LTE emissivity is equal to absorptivity, according to Kirchhoff's law. If emissivity is decreasing, absorptivity should do the same. It leads us to the conclusion, that GHGs make atmospheric absorptivity LESS, a contradiction in terms. Think again, please. -
Riccardo at 23:26 PM on 8 February 2010Increasing CO2 has little to no effect
matt sykes, #3 the effect of CO2 is mainly on the band at about 700 cm^-1 or about 15 microns while the graph you show ends at 3 microns. Also, cosider that the absorption band is relatively narrow, it's really a tiny fraction. It'd be good if you calculate it yourself approximating the incoming radiation with the Plank formula, it will probably be more convincing than my words. #4 i did not say that "it takes more than 12 hours for a photon on average to exit the atmosphere to space.". Would it be so long you couldn't have significant day/night temperature variation; just the opposite is true. The warming of the poles depends on a lot of things, not least on atmospheric and oceanic circulation. Antarctica is "isolated" both by the Antarctic Circumpolar Current and by the strong westerly winds blowing in the Southern Oceans. No one expect the same warming as in the Arctic. I do not any rough figure on the ratio between collisional and radiative de-excitation. It quite complicated and it also depends on density and temperature. You can estimate the overall effect in the atmosphere from the ratio of the energy leaving the atmosphere over energy emitted by the surface. You last claim is definitely not true as can be easily seen in the absorption spectra of CO2 from space. Indeed, at the surface level the absorption lenth is pretty short, no way to escape directly to space. -
Arkadiusz Semczyszak at 22:55 PM on 8 February 2010Could climate shifts be causing global warming?
1. In the context of the Swanson’s paper, is interesting this work: "Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate Anomaly", Trouet V. et al., 2009. "According to Trouet, a Pacific La Niña mode and a positive NAO mode could have reinforced each other in a positive feedback loop – and this could explain the stability of the medieval climate anomaly." - says one comment. La Niña ... = cool ocean = Emiliana huxleyi less and less DMS = less clouds = more heat of summer, for example as in 2003 and 2006 year (Europe)... ? 2. Human development - AGW - positive feedback in response on a natural warming? Very interesting theory ... but it has already had formerly Pielke senior. 3. Marcus say: "today, with the largest magnitude & rate of change we've seen in all of human history." This is not true. I recall once again the work of a Al Gore friend’s - L. Thompson's: "Abrupt tropical climate change: Past and Present". (proxies f. e.: delta 18O until 2003, Quelccaya). The current temperature increase is maybe unprecedented, but the former changes were violent. P.S. In Poland, the loading (abnormally long) very cold winter ... -
ConcernedCitizen at 22:41 PM on 8 February 2010Increasing CO2 has little to no effect
Sorry, final quesuiton, you say CO2 can release energy as a photon or by direct warming of other molecules. Do you have any figures for the rough percentage of energy released by each meathod? Given CO2s absorbiton band is only 8% of the total IR spectrum 92% of any release as a black body would not be re-absorbed by another CO2 molecule and thus exit the atmosphere directly. -
ConcernedCitizen at 22:36 PM on 8 February 2010Increasing CO2 has little to no effect
@Ricardo. #2 OK, lets ignore thins since no one understands my quesiton. #3 According to this, http://en.wikipedia.org/wiki/File:Blackbody-lg.png, the sun emmits far more IR then the earth at the frequencies absorbbed by CO2. Surely all this IR saturates the CO2 in the atmopshere with energy, dwarfing the IR coning form the earth? #4 OK, so you say that the CO2 primarially rleases energy as a photon of light at the same frequency it absorbed it at, and that due toi the volume of CO2 it takes more than 12 hours for a photon on average to exit the atmosphere to space. Interesting you mention the moon, its daytime high is 105`c. Is it not the case that the reason the earth has a lower daytime high is because gasses in the atmosphere, including CO2, reduce the energy that strikes the surface? As for the throry of GH gas warming dont forget the poles are supposed to warm the most, but in fact only one of them is warming, so it seems the planet earth also has a problem with the theory. I am however prepared ot accept that I am in deed missing somehting, hence asking these quesitons. -
CBDunkerson at 22:24 PM on 8 February 2010Could climate shifts be causing global warming?
Berenyi, your starting premise is redundant and incorrect. effective temperature = [(luminosity of star * (1 - albedo)) / (16 * pi * Stefan's constant * distance from star^2)]^(1/4) That is, effective temperature is the black body absorption temperature of the planet adjusted by its albedo and differing from ACTUAL temperature in that it ignores emissivity (from atmosphere and internal heat). Thus, changing albedo changes effective temperature... making your either/or scenario inaccurate, not to mention incomplete since it leaves out the actual primary driver in this case, the changing emissivity of the Earth's atmosphere. Analysis of the decrease in OLR shows that it is heavily focused within the wavelengths of radiation which are absorbed by water vapor and carbon dioxide... in short, the emissivity of the Earth's atmosphere has decreased due primarily to the increase in carbon dioxide and the positive feedback effect that has with water vapor. That said, the albedo of the planet is also decreasing (and thus the effective temperature increasing) as ice melts... another positive feedback impact from the increased temperatures driven by the CO2 increase. -
Berényi Péter at 21:12 PM on 8 February 2010Could climate shifts be causing global warming?
guys, I would like to have a straightforward answer to a simple question. If the climate system is in energetic imbalance indeed, that is OLR (Outgoing Longwave Radiation) is less than ASR (Absorbed Shortwave radiation) as a consecquence of increasing carbon dioxid contents of the atmosphere, it can happen in two ways. Either effective temperature or albedo of Earth (as seen from space) is decreasing. Which one?
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